Nakamura Y, Gotoh M, Mitsui Y, et al. - This research was sought to explore the impacts of preoperative subacromial HA injection on postoperative clinical outcome in patients with arthroscopic rotator cuff repair (ARCR). Researchers classified 98 individuals into a hyaluronic acid (HA) injection group and a non-injection group. The University of California, Los Angeles score were the functional outcome measure. They conducted univariate analysis to collect variables with p values less than 0.1; they then applied propensity score analysis, adjusting for pre- and post-operative confounding factors. Before ARCR, subacromial injection was administered to patients with worse function. It was found that after surgery, propensity score analysis successfully indicated that functional outcome was improved in patients who were administered this injection compared with patients who were not administered this injection before surgery.